Ewald Krog was born in Sejling, near Silkeborg, Denmark. After completing his primary and secondary education he went on to study Law and Latin at Aarhus University.

He is best known in Denmark for founding the public foundation Muskelsvindfonden in 1971 (Muscular Dystrophy Foundation). The aim of the organization is to improve the lives of Danes living with muscular dystrophy, a condition that Krog himself was born with. Through his work for the foundation he became well known in Denmark, both in media and as the initiator and presenter of a long running series of open air rock concerts hosted by the foundation. He stepped down as chairman of the foundation in 2016 after holding the post for a combined 42 years.

In the Lars von Trier television series Riget (1994) Krog provided the voice of the character Lillebror played on screen by Udo Kier. Due to the muscular dystrophy Krogs voice has an unusual compressed nasal quality.